JPH0774682B2 - Boiler combustion control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for a boiler, which has improved followability to load fluctuations.

[0002]

As is well known, in a combustion control device such as a steam boiler or a hot water boiler, by repeatedly controlling each stage of pre-purge, combustion and post-purge, steam or hot water To supply. That is, a sensor for detecting the steam pressure in the can or the hot water temperature in the can is provided, and a stop instruction signal is output to the burner when the detected value T rises to the set value T _OFF based on the detected value T by this sensor. , Detection value T is set value T
_The operation instruction signal is output to the burner when it descends to _ON .

[0003]

However, the conventional system may not be able to sufficiently follow the fluctuation of the load. That is, when a sudden change in the load occurs, an operation instruction signal to the burner may be output immediately after the end of the post-purge. In this case, after the post-purge, the pre-purge for the set time is performed, and then the combustion is started, so that the load following is delayed by that amount. For example, in a hot water boiler, low temperature water is supplied to the load during the pre-purge, which is a problem.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and improves the followability to load fluctuations by appropriately predicting load fluctuations and omitting the pre-purge time as much as possible. Another object of the present invention is to provide a combustion control device for a boiler. Specifically, the boiler is provided with a sensor for detecting hot water temperature or steam pressure (steam temperature), and the detected value T is detected based on the detected value T by this sensor.
Outputs a stop instruction signal to the burner when the temperature rises to the set value T _OFF, and outputs an operation instruction signal to the burner when the detection value T drops to the set value T _ON , and detects the detected value T during post-purge.
When the value falls to the set value T _ON , a pre-purge is omitted and a combustion control device that immediately outputs a transition instruction signal to combustion is provided, and a calculation means for calculating the falling gradient of the detection value T during post-purge is provided. Based on the output signal from the means, a determination means is provided to determine whether T <T _ON within a predetermined time after the end of the post-purge, and after the end of the post-purge based on the output signal from the determination means. A feature is that post-purge time extension means is provided for extending the post-purge by a preset time when it is predicted that T <T _ON within a predetermined time.

[0005]

According to the above configuration, the post-purge is performed when the falling slope of the detected value T during the post-purge is calculated and T <T _ON is predicted to be within a predetermined time after completion of the post-purge. It is possible to extend for a preset time, and when the detected value T falls to the set value T _ON during the extended post-purge, the pre-purge can be omitted and the combustion can be immediately started.
By doing so, it is possible to improve the followability to the load change by appropriately predicting the load change and omitting the pre-purge time as much as possible.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram showing an embodiment in which the present invention is applied to a hot water boiler. In the figure, (1) is a boiler, which is constructed by connecting a number of vertical water pipes (not shown) between the upper header and the lower header, for example. (2)
Is a sensor that detects the temperature of hot water. (3) is a burner, which functions to heat the water in the water pipe to heat it. The operation / stop of the burner is controlled by the combustion control device (4) based on the detection value T of the sensor (2). That is, the detected value T
When is increased to the set value T _OFF , a stop instruction signal is output to the burner (3), and when the detected value T is decreased to the set value T _ON , an operation instruction signal is output to the burner (3). The combustion control device (4) also has a function of omitting the pre-purge and immediately outputting a transition command signal to the combustion when the detected value T falls to the set value T _ON during the post-purge.

The water which has been heated by the burner (3) to become warm water is connected to a circulation pump (10) and a heat exchange pipe connected in series between the warm water outlet (8) and the warm water return port (9). Circulate through line of vessel (11). In the heat exchanger (11), heat is exchanged between the hot water and the cold water supplied from the cistern tank (12), and the heat-exchanged water becomes hot water.
It is supplied to Karan (14) through 3). This hot water supply line (1
A three-way valve (15) is inserted in (3) so that the hot water temperature of the hot water supply line (13) is constant and the cold water line (16).
The mixing ratio with the amount of cold water from is automatically controlled.

(5) is a calculating means for calculating the falling slope of the detected value T (warm water temperature) during the post-purge. (6) is
It is a judging means for judging whether T <T _ON is satisfied within a predetermined time after the end of post-purge based on the output signal from the calculating means. (7) is a post-purge time extension means, which functions to extend the post-purge by a preset time when it is predicted that T <T _ON will be _achieved within a predetermined time after the end of the post-purge.

FIG. 2 shows an example of the control circuit. The control unit (17) is composed of a microcomputer, and controls each device in accordance with a control procedure stored in advance in its internal memory or external memory. (18) is a fuel valve, (19) is a blower, (20) is an igniter, (10) is a circulation pump, (21) is an operation switch, and (2) is a sensor for detecting hot water temperature.
The circulation pump (10) is set to continuously operate while the operation control switch (21) is turned on.

Next, the operation of the above configuration will be described with reference to FIGS. FIG. 3 is a flowchart showing an example of the post-purge extension routine, and FIG. 4 is a graph showing the relationship between time and hot water temperature. First, in step S1, it is determined whether or not the post purge is started / medium. Now, in FIG. 4, time t
It is assumed that the post purge starts at ₀ . Then, the determination in step S1 is YES, the process proceeds to S2, and it is determined whether or not 25 seconds have elapsed from the start of the post-purge. The determination is NO until 25 seconds have elapsed, the process proceeds to S10, where T <T _ON (and the minimum required post-purge time has elapsed).
If there is, the pre-purge is omitted and the combustion immediately starts, otherwise, the process returns.

When 25 seconds have passed from the start of the post purge,
The determination in S2 is YES, the process proceeds to S3, where 2
The warm water temperature T ₂₅ at the time of 5 seconds is measured, this value is stored in the internal memory, and the process proceeds to S4. In S4, it is determined whether 30 seconds have passed since the start of the post purge. The determination is NO until 30 seconds have elapsed, the process proceeds to S10, and the determination process similar to the above is performed. After 30 seconds, S4
The determination is YES, and the process proceeds to S5. 30 here
The warm water temperature T ₃₀ after the lapse of seconds is measured, this value is stored in the internal memory, and the process proceeds to S6. In S6, it is determined whether to extend the post-purge time according to the following determination formula. T ₃₀ − ((T ₂₅ −T ₃₀ ) / 5 × 15) <T _{ON In} this formula, (T ₂₅ −T ₃₀ ) / 5 is the value of the temperature decrease gradient K for 5 seconds from 25 seconds to 30 seconds. And the entire left side is
It is a value calculated as to what temperature rises 15 seconds after the temperature decreases with the gradient K. If the determination in S6 is NO, the process proceeds to S9 and the post-purge ends, but S
If the determination in 6 is YES, the process proceeds to S7, and the post purge time is extended by 15 seconds. Then, the process proceeds to S8, and it is determined whether 40 seconds have passed since the start of the post purge. The determination is NO until 40 seconds have elapsed, and the process proceeds to S10. If T <T _ON , the pre-purge is omitted and the process immediately proceeds to combustion, as described above. When 40 seconds have passed, S
The determination in 8 is YES, the process proceeds to S9, and the post purge is completed.

As described above, according to the present invention, when T <T _ON is reached within the post-purge time, the pre-purge is omitted and the combustion is immediately started, and the T-purge is extended within the post-purge extension time.
When <T _ON is predicted, the post-purge time is extended, and when T <T _ON is reached within the post-purge extension time, the pre-purge is omitted and combustion is immediately started. There is. In the graph of FIG. 4, the solid line shows the change of the hot water temperature in the case of the control of the present invention, and the two-dot chain line shows the change of the hot water temperature in the case of the conventional control. As shown in FIG. It can respond quickly and realizes combustion operation that immediately responds to heat demand. Therefore, the problem that the low-temperature hot water is supplied to the load for the response delay time as in the conventional case is eliminated.

Although the post-purge extension time is set to 15 seconds in the above embodiment, it is not limited to this. Further, in the above embodiment, the accuracy of temperature decrease prediction is increased by calculating the temperature decrease gradient within 5 seconds before the end of post-purge, but the present invention is not limited to this as long as the accuracy does not matter. Furthermore, although the predicted time of the judgment formula and the post-purge extension time are set to be equal, there may be some differences. In the embodiment shown in FIG. 1, the hot water supply line
Although the hot water temperature is detected by the sensor (2) provided in (13), the hot water temperature in the can of the hot water boiler body may be detected as shown in FIG. Besides, it goes without saying that the present invention can be applied not only to the once-through hot water boiler but also to a hot water storage type hot water boiler, and is also applicable to a steam boiler (see FIG. 6). When applied to a steam boiler, the sensor (22) detects the steam pressure in the can (steam temperature is also possible), and the same combustion control as above is performed based on the detected value.

[0014]

EFFECTS OF THE INVENTION Since the present invention has the above-mentioned structure, it detects the gradient of change in the hot water temperature during post-purge,
When it is predicted that heat demand of the boiler will occur within a short time after the end of post-purge, post-purge is extended for a predetermined time, and during the post-purge extension time, the heat demand signal is received and the combustion immediately starts. can do. Therefore, it is possible to stably supply high-temperature hot water or the like without causing a response delay with respect to the heat request (improvement of followability to load fluctuation).

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an outline of a control circuit in the embodiment of the present invention.

FIG. 3 is a flowchart showing a main control operation in the embodiment of the present invention.

FIG. 4 is a graph showing changes in hot water temperature in comparison between the one to which the present invention is applied and the conventional one.

FIG. 5 is a system diagram showing another embodiment of the present invention.

FIG. 6 is a system diagram showing still another embodiment of the present invention.

[Explanation of symbols]

 1 Boiler 2 Sensor 3 Burner 4 Combustion Control Device 5 Computing Means 6 Judging Means 7 Post-Purge Time Extending Means 22 Sensors

Claims (2)

[Claims] 1. A boiler (1) is provided with a sensor (2) for detecting the temperature of hot water, and based on a value T detected by this sensor,
When the detection value T rises to the set value T _OFF , a stop instruction signal is output to the burner (3), and when the detection value T falls to the set value T _ON , an operation instruction signal is output to the burner (3) and post purge When the detected value T drops to the set value T _{ON, the} pre-purge is omitted and a combustion control device (4) that immediately outputs a transition instruction signal to combustion is provided, and the falling slope of the detected value T during post-purge is calculated. Determining means for determining whether or not T <T _ON is satisfied within a predetermined time after the end of post-purge based on the output signal from the calculating means.
(6) is provided, based on the output signal from this determination means,
A boiler equipped with a post-purge time extension means (7) for extending the post-purge by a preset time when it is predicted that T <T _ON will be _achieved within a predetermined time after completion of the post-purge. Combustion control device. 2. A boiler (1) is provided with a sensor (22) for detecting at least one of steam pressure and steam temperature in a can, and the detection value T is set based on the detection value T by this sensor. When the temperature rises to T _OFF , the stop instruction signal is output to the burner (3), and when the detection value T falls to the set value T _ON , the operation instruction signal is output to the burner (3). A combustion control device (4) that outputs a command signal for transition to combustion immediately after the pre-purge is omitted when the value falls to the set value T _ON, and a calculation means (5) for calculating the falling slope of the detection value T during the post-purge. And a judging means (6) for judging whether T <T _ON is established within a predetermined time after the end of the post-purge based on the output signal from the calculating means. After the end of the post-purge, T <T A combustion control device for a boiler, comprising post-purge time extension means (7) for extending the post-purge by a preset time when it is predicted to be turned _ON .